The world is facing problems such as the gradual extraction and depletion of petroleum reserves, and changes to the earth's atmosphere due to the greenhouse effect. In order to ensure the sustainability of human life, it has become a world trend to gradually decrease the use of petrochemical energy and petroleum feedstock and to develop new sources of renewable energy and materials.
Lignocellulose is the main ingredient of biomass, which is the most abundant organic substance in the world. Lignocellulose mainly consists of 38-50% cellulose, 23-32% hemicellulose, and 15-25% lignin. The cellulose can be hydrolyzed to form glucose. However, it is difficult for chemicals to enter the interior of cellulose molecules for depolymerization due to strong intermolecular and intramolecular hydrogen bonding and Van de Waal forces, complex aggregation, and high crystallinity of the cellulose. The main hydrolysis methods for the cellulose are enzyme hydrolysis and acid hydrolysis. However, these two technologies have obvious defects hampering their wide application.
In general, the enzyme hydrolysis can be carried out at room temperature, which is an environmentally friendly method due to rare byproducts, no production of anti-carbohydrate fermentation substances, and integration with the fermentation process. However, a complicated pretreatment process is required for the enzyme hydrolysis. In addition, hydrolytic activity is low, the reaction rate is slow, and cellulose hydrolysis enzyme is expensive. Dilute acid hydrolysis generally uses comparatively cheap sulfuric acid as a catalyst, but it must operate in a corrosion-resistant pressure vessel at a temperature greater than 200° C., thereby requiring high-level equipment. Simultaneously, the temperature of the dilute acid hydrolysis is high, the byproduct thereof is plentiful, and the carbohydrate yield is low. Concentrated acid hydrolysis can be operated at a lower temperature and a normal pressure. However, the concentrated acid hydrolysis has problems such as strong corrosivity from concentrated acid, a complex post-treatment process of the hydrolyzed solution, large consumption of acid, and difficulties for recycling, and the likes.
Accordingly, a novel method to hydrolyze the cellulose biomass is called-for.